Humic substances (HS) are ubiquitous in nature and arise from the decay of plant and animal residue in the environment. HS are among the most widely distributed natural products on the surface of the earth, and are the major organic components of soil (humus), lakes, rivers and geological deposits such as peat, leonardite, lignite (brown coal) and organic clays. Humified organic material (HOM) is relatively stable, but can vary in composition based on its location, deposit type, depth and age. HOM contains a complex mixture of organic molecules, such as bioactive polyelectrolytes (BPs).
BPs include numerous bioactive, naturally occurring, related, but not identical, high-molecular-weight polymers. Examples of BPs include, but are not limited to, fractions of HS, such as humic acid (HA), fulvic acid (FA), humin or ulmic acid (UA). The differences among BPs include a considerable variation in molecular weight and size, the number of functional groups (e.g., carboxyl, phenolic HO) and the extent of polymerization that has taken place. HA and FA have received broad international attention within the scientific community due to their wide range of bioactive characteristics. See, e.g., Drozd J., 1978, Studies of chemical and physiochemical properties of humus compounds of some taxonomic soil units, Rosprawy Naukowe, Zeszyt 13, AR Wroclaw pp. 65. BPs are useful for multiple functions in humans, other animals and plants.
Extraction of a particular BP fraction of the desired molecular functionality from HOM can be challenging. Extraction processes that are largely dependent on acid/base precursor separation via ionic exchange can dramatically alter the molecular structures of BPs, thus affecting their inherent characteristics. In addition, despite extensive research directed to understanding the formation and composition of HOM, the precise chemical structure of the constituents of HOM remains unknown. HOMs that have been isolated from different sources experienced different environments, oxidative states and humification processes, thus they typically exhibit widely varying compositions. These variations result in the production of a vast and complex array of BPs that range in molecular weights from 60 to 300,000 Da and whose polymers vary in length from a few nanometers to several microns.
Alkali extraction is a widely used method for isolation of HS from solid-phase source materials, such as soils, peat, and leonardite, as recommended by the International Humic Substances Society (IHSS). In general, HS is isolated from the solid-phase source materials by alkali extraction with aqueous NaOH, followed by precipitation of humic acid at low pH and a series of desalting steps involving cation exchange, dialysis, etc. to obtain fulvic acid. Through these procedures, all organic acids that are extracted from a solid-phase source material are ultimately found in either the humic acid or fulvic acid fraction, which may require further chemical processing prior to use.
The alkali extraction process generally only recovers approximately ½ to ⅔ of the total HOM and may alter structures of BP molecules in the extract. In addition, current alkali and acid extraction methods may present other undesirable characteristics. For example, alkali dissolves protoplasmic and structural components from fresh organic tissues, which may contaminate the HOM. Also, under alkaline conditions, auto-oxidation of some organic constituents occurs as they come into contact with air, both during the extraction and when the extracts are allowed to stand. In addition, other chemical changes can occur in alkaline solutions, such as condensation between amino acids and aldehydes and quinines, etc. These undesirable extraction features found in the conventional practices in industry preclude the use of the extracted BP materials in many downstream applications.
Thus, there is a need of an improved method for the isolation of BPs from HOMs. Embodiments of the present invention relate to such an improved method as well as related devices and BPs isolated by the improved method.